Li2CO3/Na2CO3/K2CO3及其混合熔融盐储热材料热物性分子动力学研究

对Li₂CO₃/Na₂CO₃/K₂CO₃及其二元和三元混合熔融盐的密度、比热容、黏度、热导率进行分子动力学模拟(MD),对比得出模拟结果与现有的实验数据和模拟值相近。结果表明：随着温度的升高,密度逐渐减小,离子之间的距离增加,导致对剪切应力的抵抗力变小,这说明单组分、二元和三元熔融盐黏度的负温度依赖性。对于熔融盐的热导率,单组分和二元熔融盐也呈现出负温度依赖性,而三元熔融盐趋势是随温度的升高呈上升状态。     

NTP辅助LaMnO3和La0.8K0.2MnO3催化剂脱除柴油机NOx的试验研究

基于介质阻挡放电理论设计一套低温等离子体(non-thermal plasmal,NTP)发生器。采用溶胶-凝胶法制备了钙钛矿催化剂La0.8K0.2MnO3(LKMO)和LaMnO3(LMO),并利用X射线衍射分析(X-ray diffraction,XRD)对其性能进行表征。通过柴油机台架试验,研究了NTP辅助LKMO和LMO催化对NOx的作用规律。研究结果表明:制备的催化剂形成了钙钛矿晶体结构,温度在200～350℃时,NTP辅助LMO只存在NO和NO2的吸附和脱附,而NOx总量未降低;在NTP辅助LKMO作用下,NOx浓度降低较明显,K元素的掺入提高了催化剂活性,且NTP提高了催化剂对NOx的去除效率。     

O2/CO2气氛添加CaCO3对徐州烟煤PM2.5排放的影响

采用管式炉研究了在O2/CO2气氛下添加CaCO3对PM2.5(空气动力学直径小于2.5,μm的颗粒物)排放特性的影响.试验采用荷电低压撞击器(ELPI)采集和分析燃烧后的PM2.5.结果表明,添加CaCO3是燃烧过程中影响PM2.5生成的重要因素.添加CaCO3后,生成PM1的数密度和质量浓度均降低,而PM1-2.5的数密度和质量浓度均略有增加,PM2.5粒径分布均呈双峰分布,峰值点分别出现在0.2,μm和2.0,μm左右.随着CaCO3添加质量分数的增加,PM2.5中的S、Pb、Cu、Na和K几种元素的浓度呈下降趋势.     

Superior low-temperature hydrogen release from the ball-milled NH3BH3–LiNH2–LiBH4 composite

In the present study, we employed a multi-component combination strategy to constitute an AB/LiNH₂/LiBH₄ composite system. Our study found that mechanically milling the AB/LiNH₂/LiBH₄ mixture in a 1:1:1 molar ratio resulted in the formation of LiNH₂BH₃ (LiAB) and new crystalline phase(s). A spectral study of the post-milled and the relevant samples suggests that the new phase(s) is likely ammoniate(s) with a formula of Li_2−x(NH₃)(NH₂BH₃)_1−x(BH₄) (0 < x < 1). The decomposition behaviors of the Li_2−x(NH₃)(NH₂BH₃)_1−x(BH₄)/xLiAB composite were examined using thermal analysis and volumetric method in a wide temperature range. It was found that the composite exhibited advantageous dehydrogenation properties over LiAB and LiAB·NH₃ at moderate temperatures. For example, it can release ∼7.1 wt% H₂ of purity at temperature as low as 60 °C, with both the dehydrogenation rate and extent far exceeding that of LiAB and LiAB·NH₃. A selectively deuterated composite sample has been prepared and examined to gain insight into the dehydrogenation mechanism of the Li_2−x(NH₃)(NH₂BH₃)_1−x(BH₄)/xLiAB composite. It was found that the LiBH₄ component does not participate in the dehydrogenation reaction at moderate temperatures, but plays a key role in strengthening the coordination of NH₃. This is believed to be a major mechanistic reason for the favorable dehydrogenation property of the composite at moderate temperatures.     

Releasing 9.6 wt% of H2 from Mg(NH2)2–3LiH–NH3BH3 through mechanochemical reaction

Ball milling the mixture of Mg(NH₂)₂, LiH and NH₃BH₃ in a molar ratio of 1:3:1 results in the direct liberation of 9.6 wt% H₂ (11 equiv. H), which is superior to binary systems such as LiH–AB (6 equiv. H), AB–Mg(NH₂)₂ (No H₂ release) and LiH–Mg(NH₂)₂ (4 equiv. H), respectively. The overall dehydrogenation is a three-step process in which LiH firstly reacts with AB to yield LiNH₂BH₃ and LiNH₂BH₃ further reacts with Mg(NH₂)₂ to form LiMgBN₃H₃. LiMgBN₃H₃ subsequently interacts with additional 2 equivalents of LiH to form Li₃BN₂ and MgNH as well as hydrogen.     

Steam reforming of ethanol over Co3O4–Fe2O3 mixed oxides

Co₃O₄, Fe₂O₃ and a mixture of the two oxides Co–Fe (molar ratio of Co₃O₄/Fe₂O₃ = 0.67 and atomic ratio of Co/Fe = 1) were prepared by the calcination of cobalt oxalate and/or iron oxalate salts at 500 °C for 2 h in static air using water as a solvent/dispersing agent. The catalysts were studied in the steam reforming of ethanol to investigate the effect of the partial substitution of Co₃O₄ with Fe₂O₃ on the catalytic behaviour. The reforming activity over Fe₂O₃, while initially high, underwent fast deactivation. In comparison, over the Co–Fe catalyst both the H₂ yield and stability were higher than that found over the pure Co₃O₄ or Fe₂O₃ catalysts. DRIFTS-MS studies under the reaction feed highlighted that the Co–Fe catalyst had increased amounts of adsorbed OH/water; similar to Fe₂O₃. Increasing the amount of reactive species (water/OH species) adsorbed on the Co–Fe catalyst surface is proposed to facilitate the steam reforming reaction rather than decomposition reactions reducing by-product formation and providing a higher H₂ yield.     

(La0.74Bi0.10Sr0.16)MnO3−δ–(Bi2O3)0.7(Er2O3)0.3 composite cathodes for intermediate temperature solid oxide fuel cells

(La_0.74Bi_0.10Sr_0.16)MnO_3−δ (LBSM)–(Bi₂O₃)_0.7(Er₂O₃)_0.3(ESB) composite cathodes were fabricated for intermediate-temperature solid oxide fuel cells with Sc-stabilized zirconia as the electrolyte. The performance of these cathodes was investigated at temperatures below 750 °C by AC impedance spectroscopy and the results indicated that LBSM–ESB had a better performance than traditional composite electrodes such as LSM–GDC and LSM–YSZ. At 750 °C, the lowest interfacial polarization resistance was only 0.11 Ω cm² for the LBSM–ESB cathode, 0.49 Ω cm² for the LSM–GDC cathode, and 1.31 Ω cm² for the LSM–YSZ cathode. The performance of the cathode was improved gradually by increasing the ESB content, and the performance was optimal when the amounts of LBSM and ESB were equal in composite cathodes. This study shows that the sintering temperature of the cathode affected performance, and the optimum sintering temperature for LBSM–ESB was 900 °C.     

Improved dehydrogenation properties of the combined Mg(BH4)2·6NH3–nNH3BH3 system

A combined strategy via mixing Mg(BH₄)₂·6NH₃ with ammonia borane (AB) is employed to improve the dehydrogenation properties of Mg(BH₄)₂·6NH₃. The combined system shows a mutual dehydrogenation improvement in terms of dehydrogenation temperature and hydrogen purity compared to the individual components. A further improved hydrogen liberation from the Mg(BH₄)₂·6NH₃–6AB is achieved with the assistance of ZnCl₂, which plays a crucial role in stabilizing the NH₃ groups and promoting the recombination of NH^δ+?HB^δ−. Specifically, the Mg(BH₄)₂·6NH₃–6AB/ZnCl₂ (with a mole ratio of 1:0.5) composite is shown to release over 7 wt.% high-pure hydrogen (>99 mol%) at 95 °C within 10 min, thereby making the combined system a promising candidate for solid hydrogen storage.     

Ag/Al2O3(Li2O)/g-C3N4光催化乙醇制取环氧乙烷

本文制备了一系列Ag/Al₂O₃(Li₂O)/g-C₃N₄复合催化剂,考察了其可见光催化乙醇制取环氧乙烷的性能。Li₂O可调变Al₂O₃表面的酸性,从而降低了主要副产物乙醛的选择性。Ag/Al₂O₃(Li₂O) 在g-C₃N₄上的负载量对产物环氧乙烷的选择性有较大影响,当Ag/Al₂O₃(Li₂O) 负载量为5wt%时,乙醇具有较高的转换率,且环氧乙烷的选择性高达100%。     

Oxidative steam reforming of ethanol over Ni/Al2O3 catalysts promoted by CeO2, ZrO2 and CeO2–ZrO2

Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al₂O₃ supports that were either unpromoted or promoted with CeO₂, ZrO₂ and CeO₂–ZrO₂. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO₂ and/or ZrO₂ showed that the variations induced in the Al₂O₃ by the addition of CeO₂ and/or ZrO₂ alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO₂–ZrO₂, improved catalytic activity by increasing the H₂ yield and the CO₂/CO and the H₂/CO values while decreasing coke formation. This results from the addition of ZrO₂ into CeO₂. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products.     

Synthesis,characterization, and electrochemical performance of the ternary layered composite (1-x-y) LiNi1/3Co1/3Mn1/3O2·xLi2MnO3·yLiCoO2

Composite ceramic cathodes represented by the formula (1-x-y) LiNi_1/3Co_1/3Mn_1/3O₂·xLi₂MnO₃·yLiCoO₂ were studied. A ternary compositional diagram was built with these ceramic materials as end-members, and selected points were chosen to represent the compositional space. Synthesized ceramic composite materials were investigated as to whether integration of structurally compatible units leads to improved electrochemical performance. Detailed structural (X-ray diffraction – XRD), elemental (X-ray photoelectron spectroscopy-XPS), microstructure (Scanning electron microscopy – SEM), and electrochemical (galvanostatic testing of half-cells) studies were performed and are presented. Within eight samples studied three compositions are found to exhibit first discharge capacity of around 230 mAh/g.     

Plasma-reduced Ni/γ–Al2O3 and CeO2–Ni/γ–Al2O3 catalysts for improving dry reforming of propane

Pristine Ni/γ–Al₂O₃ and CeO₂–Ni/γ–Al₂O₃ catalysts were prepared by co-impregnation technique for dry reforming of propane. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to examine the structure and morphology of the catalysts before and after the reforming reactions. The excellent interaction between catalyst active phases was observed in both CeO₂–Ni/γ–Al₂O₃ and Ni/γ–Al₂O₃ stabilized with polyethelene glycol (Ni/γ–Al₂O₃–PEG). Towards C₃H₈ and CO₂ conversion, the CeO₂–Ni/γ–Al₂O₃ and Ni/γ–Al₂O₃–PEG showed improved catalytic activity when compared to the pristine Ni/γ–Al₂O₃ catalyst. Interestingly, high H₂ concentration was achieved with the CeO₂–Ni/γ–Al₂O₃ and high CO concentration with the Ni/γ–Al₂O₃–PEG, which is due to the nanoconfinement of nickel particles within the support and favorable metal-support interaction as a result of plasma reduction. The CeO₂–Ni/γ–Al₂O₃ catalyst exhibited better stability for anti-sintering and coke resistance, thus exhibiting high reactivity and durability in the dry reforming.     

Metal-supported solid oxide fuel cells with in-situ sintered (Bi2O3)0.7(Er2O3)0.3–Ag composite cathode

Metal-supported solid oxide fuel cells (SOFCs) containing porous 430L stainless steel support, Ni-YSZ anode and YSZ electrolyte were fabricated by tape casting, laminating and co-firing in a reduced atmosphere. (Bi₂O₃)_0.7(Er₂O₃)_0.3–Ag composite cathode was applied by screen printing and in-situ sintering. The polarization resistances of the composite cathode were 1.18, 0.48, 0.18, 0.09 Ω cm² at 600, 650, 700 and 750 °C, respectively. A promissing maximum power density of 568 mW cm⁻² at 750 °C was obtained of the single cell. Short-term stability was measured as well.     

Hydrogen storage properties of destabilized MgH2–Li3AlH6 system

To improve the dehydrogenation properties of MgH₂, a novel hydrogen storage system, MgH₂–Li₃AlH₆, is prepared by mechanochemical milling. Three physical mixtures containing different mole ratios (1:4, 1:1 and 4:1) of MgH₂ and Li₃AlH₆ are studied and there exists a mutual destabilization effect between the components. The last mixture shows a capacity of 6.5 wt% H₂ with the lowest starting temperature of dehydrogenation (170 °C). First, Li₃AlH₆ decomposes into Al, LiH and H₂, and then the as-formed Al can easily destabilize MgH₂ to form the intermetallic compound Mg₁₇Al₁₂ at a temperature of 235 °C, which is about 180 °C lower than the decomposition temperature of pristine MgH₂. Finally, the residual MgH₂ undergoes a self-decomposition whose apparent activation energy has been reduced by about 22 kJ mol⁻¹ compared with pristine MgH₂. At a constant temperature of 250 °C, the mixture can dehydrogenate completely under an initial vacuum and rehydrogenate to form MgH₂ under 2 MPa H₂, showing good cycle stability after the first cycle with a capacity of 4.5 wt% H₂. The comparison between 4 MgH₂ + Li₃AlH₆ and 4 MgH₂ + LiAlH₄ mixtures is also investigated.     

Organic-inorganic composite of g-C3N4–SrTiO3:Rh photocatalyst for improved H2 evolution under visible light irradiation

The organic-inorganic composite g-C₃N₄–SrTiO₃:Rh was prepared for the first time as a photocatalyst for hydrogen production and the resulting hydrogen evolution rate under visible light irradiation from aqueous methanol solution was measured. A high hydrogen evolution rate of 223.3 μmol h⁻¹ was achieved by using 0.1 g of as-prepared photocatalyst powder comprised of 20 wt.% g-C₃N₄ 80 wt.% SrTiO₃:Rh (0.3 mol%). The hydrogen evolution rate was greater than that obtained by SrTiO₃:Rh (0.3 mol%) by a factor of 3.24. The quantum efficiency of as-prepared composite photocatalyst was 5.5% at 410 nm for hydrogen evolution. The high activity of the composite photocatalyst for hydrogen evolution stemmed from its electron–hole separation and transportation capabilities due to the hetero-junctions of the organic-inorganic composite materials. The proposed mechanism for the electron–hole separation and hydrogen evolution of the g-C₃N₄–SrTiO₃:Rh composite under visible light irradiation featured the reduced recombination of the photo-generated charge carriers. The doping of Rh ions into the SrTiO₃ has contributed to the high photocatalytic activity by forming a donor level from the valance band to the conduction band.     

石墨烯包封Na3V2(PO4)3用作钠离子电池负极材料的电化学性能探究

具有三维网络结构的NASICON型Na₃V₂(PO₄)₃材料,由于其稳定的电压平台,较高的理论容量(117 mA·h/g),被视为一种具有良好应用前景的钠离子电池负极材料。采用溶剂热和进一步热处理的方式,获得石墨烯包封Na₃V₂(PO₄)₃的复合材料[Na₃V₂(PO₄)₃/G],有效提高了Na₃V₂(PO₄)₃的电子导电性。在0.01～3.00 V电压区间,0.2 C倍率进行测试时,Na₃V₂(PO₄)₃/G复合材料在230圈循环后,其放电比容量保持在100.9 mA·h/g,容量保持率高达68.4%,即使在5 C倍率,其放电比容量仍可达65.2 mA...     

Improvement of (La0.74Bi0.10Sr0.16)MnO3–Bi1.4Er0.6O3 composite cathodes for intermediate-temperature solid oxide fuel cells

Porous composite cathodes including (La_0.74Bi_0.10Sr_0.16)MnO_3−δ (LBSM) and Bi_1.4Er_0.6O₃ (ESB) were fabricated and characterized using AC impedance spectroscopy. In our earlier work, the growth and aggregation of ESB particles were found in LBSM–ESB composite cathodes. In this study, therefore, two approaches were used to restrain the growth and aggregation of ESB particles. First, the sintering temperature of the composite cathode was reduced by introducing a sintering function layer, which caused a 22% reduction in the initial polarization resistance (R), but the cathode polarization resistance decreased at a rate of 2.15 × 10⁻⁴ Ω cm² h⁻¹ at 700 °C during a period of 100 h. Second, nano-sized Gd-doped ceria powder (CGO) was added to the composite cathode system. Stability improvement was achieved at 10 vol% CGO, and the degradation rate at 700 °C was 4.01 × 10⁻⁵ Ω cm² h⁻¹ during a period of 100 h.     

H2 and CH4 oxidation on Gd0.2Ce0.8O1.9 infiltrated SrMoO3–yttria-stabilized zirconia anode for solid oxide fuel cells

Strontium molybdate (SrMoO₃) as an electronic conductor was incorporated with yttria-stabilized zirconia (YSZ) to form an anode scaffold for solid oxide fuel cells. Gd_0.2Ce_0.8O_1.9 (GDC) nanoparticles were introduced by wet impregnation to complete the Ni-free GDC infiltrated SrMoO₃–YSZ anode fabrication. The effects of SrMoO₃ on the electrode conductivity and GDC infiltration on the catalytic activity were examined. A pronounced performance improvement was observed both on wet H₂ and CH₄ oxidation for the 56 wt.% GDC infiltrated SrMoO₃–YSZ. In particular, the polarization resistance decreased from 8 Ω cm² to 0.5 Ω cm² under wet H₂ (3% H₂O) at 800 °C with the introduction of GDC. Under wet CH₄ at 900 °C, a maximum power density of 160 mW cm⁻² was obtained and no carbon deposition was observed on the anode. It was found that the addition of H₂O in the anode caused an increase of electrode ohmic resistance and a decrease of open circuit voltage. Redox cycling stability was investigated and only a slight drop in cell performance was observed after 5 cycles. These results suggest that GDC infiltrated SrMoO₃–YSZ is a promising anode material for solid oxide fuel cells.     

Thermophysical properties and devitrification of SrO–La2O3–Al2O3–B2O3–SiO2-based glass sealant for solid oxide fuel/electrolyzer cells

Thermal behaviors and stability of glass/glass–ceramic-based sealant materials are critical issues for high temperature solid oxide fuel/electrolyzer cells. To understand the thermophysical properties and devitrification behavior of SrO–La₂O₃–Al₂O₃–B₂O₃–SiO₂ system, glasses were synthesized by quenching (25 − X)SrO–20La₂O₃–(7 + X)Al₂O₃–40B₂O₃–8SiO₂ oxides, where X was varied from 0.0 mol% to 10.0 mol% at 2.5 mol% interval. Thermal properties were characterized by dilatometry and differential scanning calorimetry (DSC). Microstructural studies were performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). All the compositions have a glass transition temperature greater than 620 °C and a crystallization temperature greater than 826 °C. Also, all the glasses have a coefficient of thermal expansion (CTE) between 9.0 × 10⁻⁶ K⁻¹ and 14.5 × 10⁶ K⁻¹ after the first thermal cycle. La₂O₃ and B₂O₃ contribute to glass devitrification by forming crystalline LaBO₃. Al₂O₃ stabilizes the glasses by suppressing devitrification. Significant improvement in devitrification resistance is observed as X increases from 0.0 mol% to 10.0 mol%.